After the penetrant has been in contact with the test surface for an acceptable period, the excess material must be removed from that surface without affecting the penetrant that has entered a defect. This is a vital stage for the surface must not be cleaned excessively or defects will be leached out. However, without proper removal of excess penetrant a high background will remain, reducing the contrast between potential defects and the test surface.
The more common methods of penetrant removal with their BS EN 571 classifications are:
